The present invention relates to an apparatus and method for applying a fluid to a moving continuous web. More particularly, the present invention relates to manufacturing cigarette filter plugs in which a moving continuous web of filter tow is coated with plasticizer using an apparatus including a multichamber cylinder control system. Known cigarette filter plug manufacturing machines may be modified to practice the present invention by removing or disabling the existing equilibrium control apparatus and adding apparatus as required for the multichamber cylinder control of the present invention.
Filter plug making machines are widely used in high speed cigarette manufacturing operations. In typical commercial filter plug makers, such as the model AF-1 made by Hauni-Werke Korber & Co AG (Hamburg, Germany), filter tow is supplied as a moving continuous web. The filter tow web is directed into an enclosed spray booth where a plasticizer, typically triacetin, is applied to the tow as a mist. The plasticizer mist is created by the spray of a spinning applicator brush. Liquid plasticizer is concurrently applied to the applicator brush through two sources: a nozzle apparatus that feeds liquid plasticizer pumped from a remote tank directly onto the applicator brush, and a reservoir which collects excess or overflow plasticizer and may be in contact with the applicator brush, depending on the level of plasticizer in the reservoir.
In the known apparatus, the applicator brush spins and picks up plasticizer from the nozzle and the reservoir. The spinning motion of the brush causes the plasticizer that has been picked up by the brush to be sprayed as a mist onto the tow passing through the spray booth. Excess plasticizer drains back into the reservoir. Equilibrium is reached when the level of plasticizer in the reservoir is constant and the rate at which plasticizer is applied to the tow is generally equal to the rate at which plasticizer is being pumped into the spray booth.
When a filter plug making machine is stopped and restarted, the renewed spinning action of the applicator brush upon start-up can create a splash from the reservoir which can damage the tow or cause it to break or wrap around the roller mechanism which transports it. This leads to a waste of tow, loss of production time, and wear and tear on the machinery.
In order to avoid splashing when a filter plug making machine is stopped and then restarted, known apparatus, such as the AF-1, drain plasticizer from the spray booth reservoir whenever the machine is stopped. In the AF-1, a 15 cc drainage cylinder and drain valve arrangement is used. When the AF-1 is shut down, approximately 30 cc of plasticizer is drained from the reservoir, lowering the level of plasticizer in the reservoir to a short distance, typically 1 mm, below the applicator brush. A portion of this plasticizer drained from the reservoir is drawn into the 15 cc drainage cylinder and the remainder is emptied out through the drain valve back to the remote tank to which the nozzle is connected. When the AF-1 is restarted, the level of plasticizer in the reservoir is below the applicator brush and the applicator brush cannot pick up plasticizer from the reservoir. Filter tow starts passing through the spray booth, however, before plasticizer is applied. Although the plasticizer collected by the 15 cc cylinder is returned directly to the reservoir, this is only a fraction of the entire reservoir capacity and the level of plasticizer in the reservoir following start-up is below the applicator brush. Additional plasticizer must be pumped into the system from an outside source before the applicator brush contacts the plasticizer in the reservoir and equilibrium is established. Typically it takes more than one minute from start-up for the known machines to replace the plasticizer lost and to reach the desired level for the plasticizer to be in contact with the applicator brush.
It is therefore a disadvantage of known filter plug making machines that only a portion of the plasticizer collected from the reservoir when the machine is switched off is returned directly into the spray booth when the machine is restarted.
Another disadvantage of known filter plug making machines is that a delay is experienced when starting-up the machine until sufficient fresh plasticizer has been pumped back into the spray booth through the nozzle to compensate for the plasticizer that has been drained out of the spray booth as a result of previously switching the machine off.
A further disadvantage of known filter plug making machines is that filter tow is wasted upon start-up because of the time required to reach equilibrium after start-up.